


Merry Gyftmas from the Bywater-Spéir-Gasters

by poppinparties



Series: No Wrong Way to be a Family [2]
Category: Undertale, Undertale (Video Game)
Genre: Christmas Fluff, Domestic Fluff, F/F, F/M, Fluff without Plot, Found Family, Gyftmas, Happy AU, No Wrong Way to be a Family Extended Universe, One Big Happy Family, Undyne has two moms, abiit (oc) is alive, chara and asriel are still here boys, not canon to my other fic but takes place within a similar universe, same ocs, the war never started again
Language: English
Status: Completed
Published: 2019-12-25
Updated: 2019-12-25
Packaged: 2021-02-25 22:35:51
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,916
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21953062
Author URL: https://archiveofourown.org/users/poppinparties/pseuds/poppinparties
Summary: Gaster spends Gyftmas day with the people closest to him. Set in a fluffy non-canon AU to my fanfic, "No Wrong Way to Be a Family".
Relationships: Minor or Background Relationship(s)
Series: No Wrong Way to be a Family [2]
Series URL: https://archiveofourown.org/series/1579015
Comments: 3
Kudos: 9





	Merry Gyftmas from the Bywater-Spéir-Gasters

**Author's Note:**

> Merry Gyftmas, everybody! I had a blast writing this fanfic, I really needed a break from the sadness to write something sugary and fluffy. While reading my other fanfic isn't really necessary to understand what's going on here, I would appreciate if you checked it out! https://archiveofourown.org/works/11047326/chapters/24627657

"Tra la la... Merry Gyftmas..."

"Merry Gyftmas to you too, River," Gaster replied, stepping off the boat at the Waterfall stop. He waved goodbye to River as he exited the cavern, passing Gerson's shop (empty for Gyftmas Day, of course), and entered the darkening lantern room. He summoned Hands to press the mushrooms as he walked down the paths, illuminating the way to the Spéir home.

The cottage looked adorable. It was decked out in lights and a decorated tree was stuck in the front yard, Gyftmas presents surrounding the base. Gaster left the presents he'd brought with the others before walking to the door of the house and knocking. It was yanked open almost immediately by a giggling Megabat child, who threw himself into Gaster's arms. Gaster laughed, hugging Caelum back tightly.

"Hello, Caelum," He greeted affectionately, ruffling his curls. "Merry Gyftmas to you." Caelum wriggled his arms free and signed _"Merry Gyftmas, Uncle Gaster!"_ Gaster grinned proudly, Caelum wasn't even four and his signing was already excellent. Caelum grabbed hold of Gaster's hand as he hopped back down to the ground, pulling Gaster along with him. 

They ran down the hall, turning around the corner and into the sitting room, where Abiit, Bayou and Undyne were decorating Gingerbread Tems. A human Christmas movie that Gaster didn't recognise was playing on the TV. Abiit looked up as the two entered the room, smiling warmly when she saw who was here. "Look what Caelum found outside!" She announced to the room as she stood up from her seat to embrace Gaster. "Merry Gyftmas, Doc!" She knocked on his skull affectionately.

"Merry Gyftmas, Gaster!" Bayou said softly with a gentle smile.

"MERRY GYFTMAS!!!" Undyne, who was clad in a Santa hat that was far too big for her, hollered. "You want some cookies? My uncle Sirius baked 'em!" Caelum nodded enthusiastically on Gaster's behalf, taking the cookie Undyne was offering and hopping up onto his mother's back so he could attempt to feed it to Gaster. The skeleton laughed, accepting the cookie in his mouth gladly. It tasted perfect. He swallowed his mouthful and called out, "Good job, Sirius!"

"Thank you!" Came the faint reply from down the hall.

"So he's on dinner duty?" Gaster asked the room as he and Abiit sat down on the sofa. Caelum moved from Abiit's shoulders and settled down on Gaster's lap instead, rubbing his face against Gaster's jumper. He giggled quietly at the text on it, which simply read "UGLY GYFTMAS JUMPER".

"Him and Lyv," Abiit replied with a nod. "If you like you can go and help them out."

Gaster fleetingly remembered the last time he'd tried to cook. Memories of his microwave exploding flashed before his eyes. He missed that microwave... with a rueful smile, he shook his head. "Ah... best not to. I'm sure you want this to be a _nice_ meal." Bayou let out a lyrical laugh. "You're banished from the kitchen too, Gaster?" she asked him. "Once I lit a pot of spaghetti on fire. I made something that was _surrounded by water_ catch fire. Lyv hasn't let me near the oven since."

Conveniently, Lyv chose that moment to enter the room, mashing a giant bowl of potatoes with determination... and a mace? She had a look on her face like she was trying to be stern, but couldn't keep herself from smiling. "Hey, babe, if you have a problem with that, you're welcome to do all this cooking prep instead of us!" Bayou blushed and shook her head. "I think I'll pass, darling," she replied quietly. Lyv leaned over the couch and kissed her on the forehead, causing the water elemental to blush even more deeply and hide her face in her hands. Undyne stuck her tongue out and turned away in disgust. Caelum stared intently and made a small heart shape with his hands.

"Eww! Those are my _moms,_ nerd!" Undyne shoved him.

 _"Cute,"_ he signed in response, sticking his tongue out at her. She jammed a cookie in his mouth, which he gladly began to eat.

For a short while, Gaster helped Abiit, Bayou and the kids decorate the Tem cookies. His artistic abilities weren't quite on par with his scientific abilities, he already knew that, but he had hoped that they could at least surpass the abilities of a three year old. He realised how incredibly mistaken he was, however, when he noticed the horrified look Caelum was giving the cookie Gaster was currently decorating.

 _"Why is Temmie bleeding?!"_ He signed frantically.

"That's her scarf," Gaster replied. Caelum gave him an incredibly skeptical look and went back to his own cookie, which did not look like Temmie had just been brutally decapitated. Gaster sighed, placing the cookie down on the plate with the other finished ones that hadn't yet been eaten. It seemed he would never make it as an artist.

 _"It's OK, Uncle Gaster,"_ Caelum signed, giving Gaster a sincere look. _"I still like you."_ Gaster smiled, and signed back. "I like you too, Caelum." Caelum glowed, snuggling further into Gaster's jumper and hugging him. Gaster hugged back, deciding then to be a freeloader and simply watch the Christmas movie instead. The pranks this strange human child was pulling were surprisingly innovative... if incredibly violent. When one of the villains was electrocuted, Gaster found himself covering his own eyes with Hands as well as Caelum's. Undyne, however, was staring at the screen, enthralled.

"Humans are so cool," she whispered to herself.

Bayou grimaced, and as she delicately tried to explain to her daughter why this movie wasn't the most _accurate_ representation of humanity, Abiit turned to Gaster. "So how are the Dreemurrs enjoying their Gyftmas?" she asked him as she absentmindely played with Caelum's hair. "We haven't heard from them since this morning."

Gaster chuckled. "Oh, they were having a wonderful time when I left this afternoon... I believe Toriel's sent me some updates, actually." He took his phone out from his pocket and checked the Undernet, seeing that he had several unread messages from the Queen of Monsters. Caelum craned his neck upwards to see as Gaster opened them, showing him and Abiit several pictures of the Royal Family. Chara was striking dramatic poses in the new leather jacket Gaster had bought them, while Asriel frantically took pictures of them with his new Polaroid camera. Little Torigore was studiously ignoring her older siblings, playing with her junior chemistry set instead. "The children seem to be enjoying their Uncle Gaster's gifts," Toriel had captioned along with a smiley face emoticon. "They say thank you."

"Aww, they look so sweet," Abiit cooed. "I can't believe how big Chara and Asriel are getting. Just feels like yesterday Azzy was born and Chara was found."

 _"Chara,"_ Caelum contributed, eyes fixated on one of the pictures of them. He was blushing faintly. He'd always had a bit of a crush on Chara. Abiit chuckled, ruffling his curls. "Yes, pup. Chara indeed."

"Are you all still coming to the palace for dinner tomorrow?" Gaster asked her. Caelum nodded enthusiastically before she could answer. She laughed, nodding as well. "Wouldn't miss it for the world."

Sirius stuck his head around the doorframe, clad in the horrible "Bone Appetit" apron Gaster had bought him for his most recent birthday. There was a large amount of stuffing stuck in his hair, which he didn't seem to notice. "Hey, Gaster," he smiled, before addressing the room. "Dinner's ready, everyone. Come in to the kitchen or get nothing!" 

Abiit stood up, suppressing a giggle at her husband's appearance as she walked towards him, but said nothing, just giving him a kiss on the cheek instead. He looked mildly confused but cheerful as he returned the kiss. Fortunately for him, he was soon spared the embarrassment of going around with food in his hair all day when Gaster walked past with Caelum hanging from his back. Caelum reached out and took some of the stuffing from Sirius' curls, popping it into his mouth and giving his father a thumbs up. Sirius laughed and walked back to the kitchen, muttering something about beating Lyv to death when Gyftmas was over.

Since Lyv and Sirius had cooked, Abiit and Bayou took over serving duty as everyone else settled down at the dining table. Gaster sat with Caelum on one side and Sirius on the other, almost salivating as he was served turkey and mashed potatoes and gravy and stuffing and dear god he wanted to dig in RIGHT NOW - but he was just about able to restrain himself, and waited patiently until everyone else had a full plate and Abiit and Bayou were seated as well. As soon as they were, Lyv gave Undyne a nod, and the small girl began to attack her food ravenously, prompting everyone else to begin eating as well. It tasted so perfect, Gaster wanted to cry.

"Lyv... Sirius..." he said between mouthfuls of food. "Would the two of you ever consider quitting the Royal Guard and becoming my personal chefs? I pay excellently. Ask my staff."

"Shut up, Gaster," Lyv replied affectionately.

Sirius looked contemplative as he chewed his mouthful of food. "Can I get weekends off?" he inquired. Lyv looked betrayed. "Absolutely," Gaster replied. "Only the best for my chefs."

"Sirius! I thought we were bros!" Lyv protested.

"Give me weekends off and I'll be your bro," he responded with a smirk. There was a thump, and he let out a pained grunt. Judging by Lyv's smug grin, she had kicked him under the table.

"Children, please, stop fighting," Abiit teasted. "Can't you be more like Undyne and Cae?" The adults turned to the two children, one of whom was currently licking her already empty plate, the other making a complicated sculpture out of mashed potato that looked a bit like an enraged pomeranian. "I mean, have you seen more well behaved under fives? I don't think so."

"It's my genes," Bayou said fondly, taking Undyne's empty plate to put more food on it. "You're made of water. You don't have genes." Gaster pointed out. Bayou waved him off, taking another Yorkshire pudding and filling it with gravy. "Technicalities."

The group of friends and family continued to talk about everything and nothing as they ate, eventually switching over to dessert when they could take no more dinner. Toriel had generously donated a Buttspie to the family, as well as the apple cake Sirius had made and the trifle the Bywaters had brought. That, along with the Gingerbread Tems they had with coffee and hot chocolate, made an excellent feast. Gaster ate and ate until he felt completely full, thanking the stars that he didn't have a stomach and could eat as much as he liked. He felt warm and comfortable and happy.

But the day wasn't over yet.

"Shall we exchange gifts now?" Gaster asked the room as he sipped his coffee. He saw Caelum and Undyne's eyes light up and instantly knew what the answer was. "Now seems like a good time," Abiit agreed, before standing up and clapping her hands. "Alright, kids, head out to the Gyftmas tree while the adults clean up in here. No touching your presents until we get out there!"

"Please, Abiit," Gaster said as Undyne and Caelum gladly ran from the room, hand in hand, giggling loudly with excitement. "Allow me. The rest of you can head on out." His eyelights glowed brightly as he spoke, and Hands began to manifest around the room, descending upon the table to collect everyone's empty mugs and plates. "Thanks, Doc," Abiit replied, giving Gaster an affectionate peck on the side of the head before heading out, the other adults in tow. Gaster stood up, directing the Hands to stack the dishes and bring them to the dishwasher, loading them inside. The ones that couldn't fit he stacked by the sink. He'd wash them later. He turned around and was surprised to see that Sirius was still there, leaning against the doorframe and giving Gaster an admiring look.

"You really are amazing," he said quietly, and Gaster blushed. "Oh, shut up, you," he brushed him off, attempting to walk past him, but Sirius caught him by the arm. "No, seriously. You are. And I don't just mean your magic. Like... thank you so much for everything you've done for us, and for sticking around. We all really appreciate you being here, Wingdin. Just... you're always welcome here, you know that? You're part of the family now."

Gaster chuckled with a soft smile, patting Sirius' hand with his own. "You're great too," he replied. "So much so that I'll forgive you calling me Wingdin." 

Both men shared a laugh before continuing down the hall, heading out the front door and into the garden, where the women and children were impatiently waiting around the Gyftmas tree.

"HURRY UP, NERDS!" Undyne yelled indignantly. Caelum nodded firmly, his arms up and his fists clenched in a determined pose. Not wanting to be nerds, Gaster and Sirius hurried up as the kids demanded, and assembled themselves around the tree. The four adults reached for the gifts that they themselves had placed under the tree and prepared to pass them around. The Bywaters would go first, then the Spéirs, then finally Gaster.

From her mothers, Undyne got a bundle of DVDs featuring cartoons and animated movies from the surface, as well as action figures of armour clad swordswomen. She hugged them her thanks. They bought Caelum a large box of candied apples, which he began to tuck into, giving the Bywaters a thumbs up as his thanks. Gaster received some expensive looking cigars, Abiit a set of throwing knives, and Sirius some expensive looking fiction books. All three of them were delighted, giving Lyv and Bayou a hug. For Bayou, Lyv had ordered an expensive and intricately framed photograph of their wedding day, and for Lyv, Bayou had bought a silver ring with a chunk of green gemstone. Peridot, it looked like. The two wives kissed their thanks, ignoring the disgusted look their daughter threw them.

The Spéirs were up next. From his parents, Caelum received a small toy kitchen set, new outfits for his Temmie plushie, and some new clothes and books. His face lit up and he signed a delighted thanks to his mum and dad, who kissed him in return. Undyne got a pair of steel toe boots (which they apparently _did_ make for four year olds) and some tough leather gloves, Bayou a box of silk scarves, and Lyv a strange and yet intricately beautiful set of armour. "Temmie armour," Sirius told her. Lyv seemed especially delighted as she noogied her thanks into her best friends' heads. For Sirius, Abiit had gotten him new coats and a pair of in-ear headphones, and he'd bought her some earrings and a knitting set. They embraced, and Gaster smiled. His friends were so cute.

Gaster examined his gift before opening it, guessing that it was a book from the rectangular shape. He was delighted to find a book of intricate puzzles and blueprints - he had never seen it before, so it must have come from the surface. "Thank you so much, you two," he said as he hugged both Spéirs. "Open it!" Abiit urged him.

Curiously opening the book, he found an envelope. When he pulled it out, Caelum looked suddenly shy, looking down at the ground and playing with his hair. Well, that solved the mystery of who this was from. He slid a finger under the lip and opened the envelope, pulling out a folded sheet of paper, which he promptly unfolded.

It was a drawing that Gaster immediately recognised as himself, dressed in his lab coat and holding something Gaster assumed was a beaker. Despite the artist being colourblind, he'd done his best to colour it in, with creative results; Gaster's eyelights were pink and his clothes were reddish-orange and blue. "#1 SCIENTIST-UNCLE" was written across the top in shaky letters.

"We helped him write it," Sirius said quietly with a smile. "The rest he did on his own." Caelum was looking hopefully up at Gaster with a nervous expression. _"Do you like it?"_ he signed. Gaster smiled, sweeping Caelum into a hug. "I love it," he replied sincerely, stroking Caelum's hair. "Thank you so much, dear child. It's perfect." Caelum let out a delighted giggle, hugging Gaster back tightly. "Love you, Uncle Gathter," he mumbled against Gaster's chest in his wavering voice. Gaster felt his soul swell. God, he adored this family.

He was so happy he had a place here. 

Sirius nudged him, startling him out of his thoughts. "Your turn, W.D," he said teasingly. Right, Gaster thought, summoning some Hands to take the bag of presents and pass them out to each person. He'd almost forgotten. "Dig in, lads." And dig in they did, Undyne, Caelum and Lyv in particular tearing into the wrapping paper with gusto.

He'd bought a pirate outfit for Undyne, complete with hat, eyepatch, stuffed parrot that could clip onto the shoulder and a plastic cutlass. He'd worried that she might find it boring, but she immediately dressed in the eyepatch and hat and ran to give him a hug. That, at least, had been a success.

For Lyv, he'd bought a leather sheath for her sword that was black and sewn with intricate silver designs, and a sharpening stone. For Bayou, he'd bought a silver necklace with a charm shaped like a shell and a matching bracelet. From the delighted looks on their faces when they opened their gifts to the rib-crushing hug he received from Lyv, he assumed they liked their gifts too.

His gifts to the Spéirs, he was most nervous about. He had spent hours thinking about what to get them, and when he had eventually decided on his purchases, they still didn't seem quite right. Gaster just hoped they would like them.

For Abiit, he'd bought a year's worth of weekly cooking lessons up in the Capital. "Because you're always telling me you wish you knew how to cook so you can do it with Sirius," he told her, before eyeballing Lyv. "I don't know about Sirius, but you'd _best_ be giving Abiit every Saturday off for the forseeable future." Lyv groaned, throwing her hands up in the air in defeat as Abiit hugged Gaster tightly. "It's perfect, Doc. Thank you so much."

For Sirius, he'd bought an expensive silver fountain pen and a notebook with a marbled cover. It hadn't felt like enough, so he'd thrown in a crate of Spider Cider for him and Abiit to share as well. Sirius seemed delighted, practically shoving his wife away from Gaster to give him a hug too.

For Caelum, he'd bought a set of picture books, each detailing beautiful locations from the surface. He'd also been lucky enough to find a painting of the night sky in the garbage dump a few months ago, and had brought it to the Capital to be restored. "For the little explorer," Gaster chuckled as Caelum tore the last of the wrapping paper and inspected his gifts. "I hope you like them, dear child, but if you don't, I have no issue replacing - "

He was cut off by Caelum launching himself into his arms and squeezing him tight, face pressed into Gaster's sweater once again. Gaster smiled softly, returning the hug as tightly as he could without hurting Caelum. Thankfully, that had been a success too. "I hope you can see all of this for real, someday," he said quietly. "The real sky, the real stars, everything." He'd spoken softly enough that the Bywaters didn't hear him, but Sirius and Abiit gave him gentle, sad looks. That was what they wished for their child too. Moving as one, they joined the hug, and then Undyne clambered on top of them, prompting her mothers to join in too. They were one giant seven person sandwich, and they couldn't be happier.

That evening, after all the gifts had been brought inside and the wrapping paper cleaned up, the family of seven settled down in front of the TV to watch more movies. This one Gaster had seen before, about the Grinch that had stolen Christmas. Undyne bared her teeth everytime the Grinch appeared on screen. "When I grow up, I'm gonna find mean guys like the Grinch and _BEAT 'EM ALL UP!!!"_ Caelum nodded sagely. _"I'll help,"_ he signed. Undyne cheered and high fived him, and they got up off their parents' laps to play Beat up The Grinch with Undyne's new action figures. The adults, finding this creative game far more interesting than the movie, turned to watch.

The evening continued like this, watching silly movies and eating Gingerbread Tems and chocolate and watching the kids play, until at last Undyne had tired herself out, flopping out onto the floor like a blobfish and closing her eyes. Bayou laughed and gently scooped her up from the floor. "I think it's time for bed, guppy," she said quietly, stroking her daughter's hair. Undyne murmured something sleepily and waved to Gaster and the Spéirs. "Merry Gyftmas... nighty night..." she mumbled, eyes already sliding closed. The Bywaters exchanged hugs and promises to meet up the next morning before heading to the Dreemurrs' for the day, and took their leave, leaving Gaster alone with the Spéirs.

"Should I leave as well?" he asked them. "If you'd like to be alone for the last few hours of Gyftmas, I completely understand."

Caelum shook his head violently, curls bouncing. Sirius laughed, touching his head softly. "Well, Cae's got the right idea," he replied. "You're part of the family now, Uncle Gaster, whether you like it or not. And family stays as long as they please."

"Or as long as we make them," Abiit chimed in, wrapping an arm around Gaster and resting her head on his shoulder. "You're our prisoner now, Doc. You're gonna live in our house _forever."_ Gaster chuckled, clearly someone had already started on the Spider Cider. "Do I at least get a nice cell?" He inquired jokingly. "Oh, the _best."_

Sirius rolled his eyes, suppressing a laugh. "What this idiot means is we have a spare room and you're welcome to spend the night if you'd like." Abiit swiped at him with a couch cushion, hitting him square in the face. Caelum giggled from his lap, and he sighed. "Stop that, wife. You're encouraging our child to do violence." Caelum took another sofa cushion and tapped it against his face. "See! It's already started!"

Gaster laughed, relaxing back into the couch, gladly accepting the invitation to spend the night. He probably could have stayed here forever. Had it really only been a year since he'd befriended the Spéirs? Yes, Caelum's surgery had been in January... At first his visits to the family had strictly been to check on how Caelum was doing, to see if he needed anything. He couldn't even pinpoint when they had become something more, when he'd been visiting just for the sake of seeing people he cared about... people he loved. When he had gone from "Doctor Gaster" to "Doc, W-D, Uncle Gaster." But he couldn't have been more happy that things had gone this way. For the first time in years, it felt like he had a family.

For the first time in years, he'd had a Gyftmas that felt like he truly belonged.

**Author's Note:**

> I hope you enjoyed! If you did, a kudos would be very much appreciated, a comment even more so. Thanks so much for reading! I hope Sansta didn't bring anyone a bad time for Gyftmas!


End file.
